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Finding the Fourth Proportional to 428.90, 643.65 and 212.63

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Solution

The fourth proportional to 428.90, 643.65 and 212.63 is: 319.09

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.90 : 643.65 = 212.63 : x
  2. Step 2: Convert to fraction form
    428.90/643.65 = 212.63/x
  3. Step 3: Cross multiply
    428.90x = 643.65 × 212.63
  4. Step 4: Simplify right side
    428.90x = 136,855.28
  5. Step 5: Solve for x
    x = 136,855.28/428.90
  6. Step 6: Final answer
    x = 319.09

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.